 |
AN OVERVIEW OF THE AQUATIC INSECTS IN MANITOBA Terry D. Galloway Department of Entomology, Faculty of Agricultural and Food Sciences University of Manitoba, Winnipeg, Manitoba April 19 , 2007
I have retooled this information together from various sections of a lab manual in a course I offer in Introductory Entomology at the University of Manitoba. I have also added a bit of information here and there where I thought it might be relevant to people who are interested in aquatic insects from an environmental perspective. I wanted to provide you with some very basic information about many of the aquatic insects you may have encountered yourself, read about, and which have proven important in monitoring the health of aquatic ecosystems. Hopefully there will be something in this account that will be of interest to you. Insects have successfully invaded aquatic habitats of nearly every kind. They are found in streams, rivers, ponds and sloughs, lakes, temporary pools, and water trapped in the specialized leaves of carnivorous plants ( e.g. pitcher plants). They are found in saline ponds and hot springs. The larvae of one species of ephydrid fly even live happily in seepage pools of crude oil! The only aquatic habitats in which insects are not dominant are the seas and oceans where other invertebrates ( e.g. crustaceans, annelids and molluscs) are of major importance. However, there are many species found in the coastal salt marshes and tidal flats, there are sucking lice which have specialized as ectoparasites of seals and there are chewing lice on sea birds. The ocean skaters (close relatives of the water striders) have abandoned association with the land altogether and are found on the surfaces of the open seas. Aquatic insects live in the sediments at the bottom, they are free-swimming in the water column, they cling to the rocks and vegetation, hang beneath the surface and travel on the water supported by the surface tension. There are many species that are considered to be semi-aquatic, in that they inhabit the margins of ponds, lakes and streams, or perhaps even skip about over the leaves of emergent plants. Aquatic plants, too, are attacked by some insects, and larvae of these species may be found burrowing and tunneling through their stems, leaves and roots. A larvae of a few species of highly adapted insects have specialized structures they use to tap into the tissue of aquatic plants to obtain air to breathe while submerged.
In Manitoba, we have five orders of insects which are strictly aquatic, and nine more which have entire families or groups of species which are aquatic. There are approximately 90 families of insects in which there is at least one aquatic or semi-aquatic species. Obviously I can = t include all these families here. However, I have chosen the following orders and families to provide you with exposure to some of the most common aquatic groups found in Manitoba or to families which have particularly interesting and unusual adaptations to aquatic habitats.
I have added several families of aquatic Diptera which include species which are blood-feeders as adults, and which are some of our most important pests. These include some of our most familiar insects, those that come looking for you as you stand at your barbecue, helping to bring you closer to and deepen your appreciation of nature. Many families have no officially designated common names. In each case, the common name is usually a form of the family name. At the end of each section on a particular group of aquatic insects, I have provided an assortment of references that you might find valuable if you would like additional, more specific information.
1. Order - Ephemeroptera (mayflies) Eph-em-er-OP-ter-a This order is represented by at least 12 families in Manitoba, all of which are aquatic in their juvenile stages. There are approximately 80 species recorded for the province so far, with many more undoubtedly awaiting discovery. There is some information available on the emergence patterns of many species. However, details of the life histories of our Manitoba mayflies are known for only a handful of species. Mayflies are unique in that they are the only hemimetabolous order in which the adult forms shed their skin, or moult. There is a fully winged terrestrial form, the subimago , which emerges from the aquatic nymph. The imago is the sexually mature adult form that emerges following the moult. You may have seen the wispy, gray cast skins of the subimagoes floating about on the wind when there has been a mass emergence of burrowing mayflies. There are a few species in Manitoba which have such a short adult life span that they do not undertake the imaginal moult. Ephoron album , for example, is a beautiful, pale species of burrowing mayfly that emerges in enormous numbers from the shallow riffles of streams in late July to mid-August. The adults begin to emerge just after dark, live for just a few hours, mate, lay their eggs and then die. Next morning, if you walked along the river bank, the only evidence of the night = s emergence might be a few adults trapped in spiders = webs. Adult mayflies are conservative in general appearance, all being delicate and soft-bodied, usually with four triangular wings, most often with many veins and cross-veins. These wings are held like sails, vertically over the body at rest. The antennae are very small and thread-like; the legs are usually long and slender. There are two (or in the cases of the immatures, three) long, slender tails trailing from the end of the abdomen. Mouthparts are vestigial, and the adults are not known to feed. This is the group that is most noted for its short adult lifespan - from a few hours in some species, to a few days (hence the name of the order, i.e. , ephemera=brief; ptera=wing, literally in a winged stage for only a short time). The most familiar species for Manitobans are the burrowing mayflies, Hexagenia spp. These mayflies swarm in enormous numbers from the Red River, Lake Winnipeg, Dauphin Lake, and other bodies of water where the sediments are soft and muddy. They fly mainly at night and are strongly attracted to lights. In some places, they may be so abundant that they create a hazard on the roads and bridges where their bodies accumulate, having been pulverized into slime by passing vehicles. There can be such enormous numbers at lights that they have to be cleared away with front-end loaders. While the adults may be conservative, the aquatic nymphs are extremely diverse. They are adapted to living in almost every conceivable aquatic habitat, and have anatomical features which provide valuable service. There are severely flattened forms found clinging to rocks in torrential streams; there are bullet-shaped super swimmers, which look more like minnows than insects as they swim, that are active in fast moving water; there are tusked and hairy species that burrow in soft sediments; there are free-swimming species found in ponds and lakes. Most are detritivores and/or herbivores and feed by scraping, grazing or filtering fine particulate organic matter and algae. As you can imagine, the overall appearance of the immature stages is difficult to generalize. However, the antennae are usually long and thread-like, the eyes are well developed, there are wing-pads at the back of the thorax, and there are numerous pairs of delicate gills on the abdominal segments. The abdomen usually terminates in three (sometimes two) long filaments. At the end of each leg, there is just one tarsal claws. This group of insects is an important source of food for fish, many of which are valuable game fish species ( e.g. pickerel). Because the juvenile stages live in the water and may take two years or more to complete their development, they are also sensitive to changes in water quality, and are valuable indicators of environmental changes brought about by human activity. The introduction of chemical pesticides and fertilizers, runoff from livestock operations, or suspended sediments can have disastrous affects on populations of many species of mayflies.
References to Manitoba Ephemeroptera: Alba-Tercedor, J., and J. Flannagan. 1995. Two new Canadian species of the genus Tricorythodes Ulmer, with additional studies on other North American species (Insecta, Ephemeroptera: Leptohyphidae). Canadian Journal of Zoology 73: 1588-1598. Campbell, I.C. (ed.). 1990. Mayflies and Stoneflies: Life Histories and Biology. Kluwer Academic Publishers, Dordrecht, The Netherlands. 366 pp. Cobb, D.G., T.D. Galloway, and J.F. Flannagan. 1991. Life history adaptations of mayflies to an unstable reach of Wilson Creek, Manitoba, Canada. In: Overview and Strategies of Ephemeroptera and Plecoptera, (Eds.) J. Alba-Tercedor and A. Sanchez-Ortega, Sandhill Crane Press, Inc., Gainesville, Florida. pp. 465-481. Corkum, L.D., and J.J.H. Ciborowski (eds.). 1995. Current directions in research on Ephemeroptera. Canadian Scholars' Press Incorporated, Toronto. 478 pp. Edmunds, G.F., S.L. Jensen and L. Berner. 1976. The mayflies of North and Central America. University of Minnesota Press, Minneapolis. Flannagan, J.F. The burrowing mayflies of Lake Winnipeg, Manitoba, Canada. In: Proceedings of the 2nd International Conference on Ephemeroptera. (Eds.) K. Pasternak and R. Sowa, Panstowe Wydaunictwo Naukowe, Warsaw-Krackow, Poland. pp. 103-114. Flannagan, J.F. and D.G. Cobb. 1984. Production of Hexagenia limbata (Serville) and H. rigida McDunnough in Lake Winnipeg. In: Proceedings of the IVth International Conference on Ephemeroptera. (Eds.) V. Landa, T. Soldan and M. Tonner, Bechyne, Czechoslovakia, CSVA, Ceske Budejovice. pp. 307-315. Flannagan, J.F., D.G. Cobb and M.K. Friesen. 1990. The relationship between some physical factors and mayflies emerging from South Duck River and Cowan Creek, Manitoba. In: Mayflies and Stoneflies: Biology and Life Histories. (Ed.) I. Campbell, Junk, The Hague. pp. 233-242. Giberson, D.J. and T.D. Galloway. 1985. Life history and production of Ephoron album (Say)(Ephemeroptera: Polymitarcidae) in the Valley River, Manitoba. Canadian Journal of Zoology 63: 1668-1674. Heise, B.A., J.F. Flannagan, and T.D. Galloway. 1988. Production of Hexagenia limbata (Serville) and Ephemera simulans Walker (Ephemeroptera) in Dauphin Lake, Manitoba, with a note on weight loss due to preservatives. Canadian Journal of Fisheries and Aquatic Sciences 45: 774-781. Heise, B.A., J.F. Flannagan, and T.D. Galloway. 1987. Life histories of Hexagenia limbata (Serville) and Ephemera simulans Walker (Ephemeroptera) in Dauphin Lake, Manitoba. Journal of the North American Benthological Society 6: 230-240. Kondratieff, Boris C. (coordinator). 2000. Mayflies of the United States. Jamestown, ND: Northern Prairie Wildlife Research Center Online. http://www.npwrc.usgs.gov/resource/distr/insects/mfly/index.htm . Scudder, G.G.E. 1975. An annotated checklist of the Ephemeroptera (Insecta) of British Columbia. Syesis 8: 311-315.
2. Order - Odonata (dragonflies, darners, skimmers and damselflies) O-don-A-ta Adult odonates are familiar to anyone who has gone for a summer-time stroll along the edge of a stream, pond or lake in Manitoba. They are easily the masters of flight in the insect world, with their gentle grace and sudden dashes; they are among the few species that can hover endlessly, and even fly backwards. There are 8 families and nearly 100 species known to occur in Manitoba. The adults are immediately recognized by their enormous compound eyes, tiny filamentous antennae, and elongate abdomen. Many species are brightly coloured - blue, green, red or spotted. Sadly, the brilliant colours in the adults of most species fade or change in hue once they have died and pinned. The four wings cannot fold, but are held perpendicular to the body at rest in the case of dragonflies, and parallel to the body in damselflies. The segments of the thorax are tipped forward so that the spiny legs come together to form a basket. They use this basket to scoop up other insects (even other dragonflies) from the air, and carry them away to a perch to munch on them quietly. All of our species are aerial predators. They also have a rather unusual mating system. The males have an accessory organ at the base of the abdomen, and terminal claspers. First a male will place a packet of sperm, the spermatophore , into his own accessory organ. It then conducts an elaborate courtship flight to display his fitness as a suitable mate. When a female finally accepts the male, he grasps the female by the back of the head using his claspers. The female then brings the tip of her abdomen forward to the accessory organ where she receives the spermatophore. The pair will often fly about in tandem, sometimes for hours until the female has laid a batch of eggs. The nymphs are all aquatic and predacious. We have species that live in fast riffles and in stream margins; however, the majority are found in standing water, ponds, sloughs, and lakes. They may sprawl on the bottom, hidden among the debris, waiting for their prey, or they may climb about the vegetation, stalking their prey. The nymphs of damselflies are most abundant in submerged vegetation, but they commonly swim through the water with an awkward-looking side-to-side motion, legs extended. The labium is hinged and folds back to form a mask, normally concealing a frightening pair of chewing mandibles (odontos=tooth). They can shoot the labium forward and grasp passing animals, including small fish and tadpoles, using lateral lobes which function like pincers. The legs are well developed; wing pads are present on the thorax; there are no lateral gills on the abdomen. Damselflies have three flattened, blade-like gills attached to the end of the abdomen; dragonflies have internal gills which cannot be seen from the outside. There is a chamber that surrounds these gills, and water is drawn in and out. Many species can force the water out with enough pressure to give them modest jet propulsion. Juvenile dragonflies must crawl out of the water before the adult can emerge. Some will climb vertical surfaces, and the adult will emerge from the juvenile skin, using the forces of gravity to help it to complete the moult. The shed skins are often seen left behind clinging to a plant, dock piling or boathouse, after the adult has flown away. Other species will emerge from a horizontal surface, and may crawl only a few centimetres from the edge of the water before they complete their moult.
References to Manitoba Odonata: Ackerman, J. and T.D. Galloway. 2003. Odonata larvae in urban retention ponds in Winnipeg, Manitoba, Canada. Proceedings of the Entomological Society of Manitoba 59: 5-15. Acorn, J. 2004. Damselflies of Alberta. Flying Neon Toothpicks in the Grass. University of Alberta Press. Conroy, J.C. and J.L. Kuhn. 1977. New annotated records of Odonata from the province of Manitoba with notes on their parasitism by larvae of water mites. The Manitoba Entomologist 11: 27-40. Dunkle, S.W. 2000. Dragonflies through binoculars. A field guide to the dragonflies of North America. Oxford University Press. viii + 266pp. Hughes, M.L. and J.R. Duncan. 2003. The dragonflies of Manitoba : an updated species list. The Blue Jay 61: 168-175. Manitoba Dragonfly Survey and NatureNorth.com. 2006. Dragonflies of Manitoba. http://www.naturenorth.com/dragonfly/index.html. Walker, E.M. 1912. The Odonata of the Prairie Province of Canada. The Canadian Entomologist 44: 253-266. Walker, E.M. 1933. The Odonata of Manitoba. The Canadian Entomologist 65: 57-62. Walker, E.M. 1941. New records of Odonata from Manitoba. The Canadian Entomologist 73: 35-36.
Family - Agrionidae (suborder - Zygoptera; broad-winged damselflies); Ag-ri-ON-i-dae The agrionids are a small family of damselflies, represented by only one species in Manitoba, Agrion aequabile (Say), but its eastern relative, A. maculatum Beauvois, may also be found here. These insects are rather unusual in that they are found only in running water, whereas most of the other damselflies are found in a variety of aquatic habitats. The nymphs have extremely long legs, long antennae, and long pointed gills. They are poor swimmers, but maintain their position in the stream by hiding in the vegetation along the edges. The second reason is that the adults are so strikingly beautiful! The body is a metallic blue-green, and the wings are smoky to jet black. The adults are not particularly good fliers, but rather flutter along the stream margins, more like butterflies. If you get a chance to stop on a sunny late summer day at the Brokenhead River and the TransCanada Highway, you are almost certain to observe these remarkable damselflies. Depending on the reference you read, this family is sometimes referred to as the Calopterygidae, and the type genus is Calopteryx , rather than Agrion for the family Agrionidae.
Family - Coenagrionidae (suborder - Zygoptera; narrow-winged damselflies); Coen-ag-ri-ON-i-dae The coenagrionids, about 20 species of which occur in Manitoba, are our most frequently encountered damselflies. They are found in a wide variety of aquatic habitats, mostly standing water, though they are also found in quiet backwaters along streams and rivers. They are mostly small, delicate damselflies, with slender blue or green bodies. The abdomen is so slender, that the name toothpickflies is sometimes given to the family. Nehalennia irene (Hagen), in particular, is the smallest species in the province, but has a striking combination of colours. Like the agrionids, the narrow-winged damselflies are poor fliers, and flutter about on sunny days, sometimes in considerable abundance. The nymphs do not swim effectively, but tend to hide in aquatic vegetation. If you do see them swim, they move by thrashing their bodies from side to side, but make little progress. Members of this family are similar in colour and general to those in the family Lestidae, which have slightly different wing venation and a few additional subtle differences.
Family - Aeshnidae (suborder - Anisoptera; darners, devil's darning needles); AESHN-i-dae These large and striking dragonflies are common in Manitoba, and are represented by at least a dozen species in the province. They have incredible powers of flight, and frequently become the obsession for students studying Insect Taxonomy in our Department. They can be extremely difficult to capture, and students will swear that these dragonflies will make repeated deliberate passes at them, and then veer away just out of reach of a desperate swing of the net. The cunning entomologist waits until dusk, as the dragonflies take up their night-time perches in the long grass, and when disturbed, fly only on couple of metres away before landing again. If you can't wait for dusk, and if there are hunting aeshnids in the air, you can sometimes attract them to you by taking a long grass stem and stripping off all the head except for the tip. Reach up and dangle the tip like a fishing lure, and you will get these hungry predators zooming in at you. The aeshnids are very aggressive predators both as adults and as nymphs. The adults cruise along, scooping up unsuspecting flying insects up to a considerable size, including large butterflies and other dragonflies. They get their common names from the old superstition that if a person used foul language or told a lie, the Devil would send in these agents in to sew your lips together. The full-grown nymphs stalk their prey, and happily feed on small fish and tadpoles.
Family - Libellulidae (suborder - Anisoptera; common skimmers); Li-bell-UL-i-dae We have at least 20 species of skimmers in the province, and they are often extremely common and found in all kinds of aquatic habitats. The adults are mostly medium-sized dragonflies, brightly coloured red, black, blue, yellow and white. The males typically set up territories along the pond margin. They then establish several perches from which they can survey their territory and defend it against all intruders. The fact that they return habitually to the same perch has been the undoing of many specimens that now reside in our museum collection. Occasionally, some species occur in spectacular numbers. Libellula quadrimaculata L. sometimes appears in the millions along the shores of the Manitoba Great Lakes. When this happens, the insectivorous birds, mammals and aeshnids have a feast. The nymphs are mostly sprawling predators which lie about on the bottom, patiently waiting for their next meal to pass by.
3. Order - Plecoptera (stoneflies) Plec-OP-ter-a We have 7 families of stoneflies in Manitoba, all of which have aquatic juvenile stages. There are about 40 species of stoneflies recorded for Manitoba, many of which are quite rare or limited in distribution. Capnura manitoba (Claassen), for example, was described from Aweme (near Treesbank) back in 1924 (as Capnia manitoba ), yet the only records for this species subsequent to its discovery came from eastern North America. It wasn't until 1982, that a student in our Department, Dave Burton, did some detective work with the original descriptions and topographical maps, and rediscovered C. manitoba in tiny springs that run into the Assiniboine River near the historical site of Aweme. To this day, these are the only known sites for this species in Manitoba. Another species, Megaleuctra stigmata (Banks), is recorded from Manitoba, but we still do not know if the early records are in error, if the species is extinct in the province, or if this montane species still resides in a relict spring habitat somewhere. The stoneflies are an intriguing group of aquatic insects, and there is a great deal of research that remains to be done on our Manitoba species. Most of our species are found in rivers and streams, but you may find them on occasion on the rocks of wave-swept lake shores. The adults live for only a short time, but may feed using their chewing mouthparts. They are soft-bodied, and the four wings are folded together flat over the body at rest (pleckto=plait, weave; ptera=wings). Adults retain two terminal abdominal cerci, but these may be hidden from above if the wings are fully developed and folded over the abdomen. We have a few species in which some individuals, or one sex or the other may have shortened wings ( brachypterous ) or no wings at all ( apterous ). We have quite a number of winter stoneflies in Manitoba. These species emerge as adults in March and April, sometimes when there is still ice on the rivers. The adults crawl through cracks in the ice onto the snow to mate and disperse, before they crawl back down to lay eggs. Adults of our species have characteristic drumming patterns that they exhibit as a means of mate location and identification. Potential mates use hardened plates on the underside of the abdomen to strike the surface they walk on. The pattern of vibrations set up by this drumming behaviour is used in species recognition and mate location. Most nymphs are elongate and cylindrical, with chewing mouthparts and long slender antennae. The legs are well developed with two terminal tarsal claws on each. There may be nests of white filamentous gills at the bases of the legs, on the abdomen, or even on the mouthparts of some species. There are two cerci at the tip of the abdomen. Most stonefly nymphs are detritivores or herbivores, scraping or shredding coarse particulate organic matter. However, several of our Manitoba species are large, hulking predators, feeding on a variety of other aquatic invertebrates. Many of these predacious species take two or more years to complete one generation. Stonefly nymphs play a significant role in detritus processing in Manitoba streams. That means that they convert the energy tied up in organic matter, and make some of that energy available at other levels in the food chain. As with many groups of aquatic insects, the stoneflies are sensitive to environmental change. Since most species of stoneflies are poor dispersers, or have multiyear life cycles, if they are decimated by pollutants or contaminants in the stream, their recovery under favourable conditions may be slow.
References to Manitoba Plecoptera: Burton, D.K. 1984. Distribution of Manitoba stoneflies (Plecoptera). Proceedings of the Entomological Society of Manitoba 40: 39-51. Flannagan, J.F. and D.G. Cobb. 1991. Emergence of stoneflies (Plecoptera) from the Roseau River, Manitoba. American Midland Naturalist 125: 47-54. Friesen, M.K., J.F. Flannagan and D.G Cobb. 1984. Emergence of stoneflies (Plecoptera) from South Duck River and Cowan Creek in the Duck Mountain region, Manitoba. American Midland Naturalist 111: 69-80. Kondratieff, Boris C. and Richard W. Baumann (coordinators). 2000. Stoneflies of the United States. Jamestown, ND: Northern Prairie Wildlife Research Center Online. http://www.npwrc.usgs.gov/resource/distr/insects/sfly/index.htm.
4.
Order - Hemiptera (true bugs) Hem-IP-ter-a The Hemiptera is a large order with at least 31 families present in Manitoba. All members have sucking mouthparts, with a long curved rostrum appearing to originate at the front of the head, running back and often extending to between the legs. The front wing (or hemelytron ) is unique among the insects in that the base (made up of the cuneus , corium and clavus ) is thickened and leathery, while the distal portion is membranous (hemi=half; ptera=wings). The hindwing is entirely membranous, and folds up underneath the hemelytra to lie flat over the back. This system for recognition of hemipterans is not entirely fool-proof because there are apterous (a=no; ptera=wing) species and juveniles are wingless, but it will do for most Manitoba representatives. Most hemipterans are terrestrial and feed on plants, injecting saliva into the plant and sucking up plant fluids. There are a number of predacious species which feed primarily on other insects, though some feed on the blood of vertebrates. We also have many well-known aquatic species in the province, some of which may be extremely abundant. Most of the aquatic species are predacious, feeding on other aquatic invertebrates, small fish, tadpoles or even snakes and frogs, while some are herbivores/detritivores. Most adult hemipterans have scent glands with openings somewhere on the underside of the thorax. When disturbed, they can let go with some really unpleasant combinations of odours.
References to Manitoba Aquatic and Semiaquatic Hemiptera: Brooks, A.R. and L.A. Kelton. Aquatic and semiaquatic Heteroptera of Alberta, Saskatchewan, and Manitoba. Memoirs of the Entomological Society of Canada, No.51. Scudder G.G.E. 1987. Aquatic and semiaquatic Hemiptera of Peatlands and marshes in Canada. Memoirs of the Entomological Society of Canada 140: 65-98.
Family - Gerridae (water striders, pond skaters); GERR-i-dae The water striders are familiar insects for Manitobans, who sometimes mistakenly call them water spiders. We have 7 species of gerrids in the province, most of which are found on ponds and quiet streams or backwaters. They have the remarkable ability to smoothly row their way across the water surface, and look like they should be so easy to catch - until you try. They can really motor when pursued, and they will switch gears into a frantic hopping, jumping strategy if you start to get close. They will go on land or vegetation, where they are quite difficult to see. They feed non-selectively on insects trapped in the surface tension, and they can detect the direction of vibrations created by a struggling insect. If the trapped insect is large, a dragonfly, for example, you may find several dozen water striders all lined up around the fallen insect, each with their beak extended and feeding. Most of our species of gerrids have fully developed wings. However, those species found on streams and rivers have a higher proportion of wingless individuals, or they may be entirely apterous. The males of one species, Rheumatobates rileyi Bergroth, are so incredibly modified as to be hardly recognizable as a member of this family. They have bizarre antennae, and their hind legs look like they have been broken and reshaped into add angles and curves. This species, sometimes called a riffle bug, congregates on the surface in the fast, rushing water behind rocks. They swarm around rapidly over the surface, and at first glance, they don't look like they are touching the water at all.
Family - Nepidae (water scorpions); NEP-i-dae Although there are two species of water scorpions recorded in Manitoba, only one, Ranatra fusca Palisot de Beauvois, is commonly encountered. This insect is very easily recognized, with its long, stick-like body and legs, raptorial front legs, and long thin respiratory tube at the posterior end. This breathing tube is made up of two independent halves which normally are interdigitated; occasionally in dry specimens you will find that these two halves have come apart, so it is difficult to understand from what you see how the structure functions as a snorkel. Water scorpions are all predators, and they hide in the vegetation of ponds or quiet streams, lying in wait for their prey. They will feed on any animals that are suitable in size, including aquatic insects, crustaceans, small fish and tadpoles. Our species inserts its eggs into plant tissues under water, and probably completes only one generation per year.
Family - Belostomatidae (giant water bugs); Bel-o-sto-MAT-i-dae We have three species of belostomatids in Manitoba, two of which are quite common in ponds and quiet streams. The largest of the three, Lethocerus americanus (Leidy), is a ferocious looking bug, over 5cm long, that is most frequently seen in the spring (especially) and late summer when it flies to lights during its dispersal flights. They often become stranded, lying on their backs, on the pavement on sidewalks and parking lots. The females lay their eggs in a cluster of 50 or more on stems of emergent vegetation. When the eggs are above the water line, the females lurk below the surface, periodically climbing up over the cluster to drip water over the eggs to keep them moist. They will also rise from the water to defend their eggs from predator attack, so be a little careful if you decide to examine the eggs closely. People are frequently afraid of these bugs, perhaps with some good reason - they can inflict an extremely painful bite, often followed by considerable swelling and discomfort. When you pick these bugs up, handle them with caution. They are active predators, and the adults can feed on quite large prey. I have seen them feeding on snakes, and I have seen them capture and kill frogs for food. The smaller of our common species, Belostoma flumineum Say, has interesting mating behaviour, and the eggs are cemented by the female onto the back of the male. The male carries the eggs about until they hatch.
Family - Notonectidae (backswimmers); Not-o-NECT-i-dae All 6 species of notonectids in the province are easily recognized in the field by their habit of swimming on their backs beneath the water surface. Both adults and nymphs swim in the same way, with rather jerky motions according to the strokes of the modified back legs. The dorsal surface of these bugs is white or at least light-coloured and mottled, the opposite pattern observed in most aquatic animals. However, because of their unusual swimming behaviour, the benefits of cryptic colouration are still evident. The backswimmers are very active insects, and feed on a wide range of prey items. They have even been investigated as possible biological control agents of mosquitoes. They will bite if they are handled carelessly, but the pain is nothing like that inflicted by their belostomatid cousins.
Family - Corixidae (water boatmen); Cor-IX-i-dae The water boatmen are some of our most curious looking aquatic insects. They have broad flat heads, somewhat flattened bodies, scoop-shaped front tarsi, intricately patterned forewings, and highly modified hind legs for swimming. There are over 40 species in the province, mostly in ponds and still backwaters of every kind. Some species even seem to be best adapted to living in saline sloughs. In the fall, they often disperse into larger rivers and streams, and will literally cover the bottom. If you step into the water, the bottom seems to move with these thousands of individuals, usually composed of dozens of species. In the spring, after the ice has melted, there may be absolutely massive dispersal flights on the first warm days, and the air will be filled with these little guys looking for a new place to live. I once was on my way late at night with Don Cobb to visit a stream in the Riding Mountains. When we passed a small service station near the town of Riding Mountain, we noticed that there was a group of teenagers shrieking and dancing around the gas pumps at the station. We pulled in to have a look, and to our surprise there was a water boatman blizzard around the lights at the pumps. The numbers were truly impressive. Having satisfied out curiosity, we completed our drive, got out of the truck, and when I looked back into the truck to remove some gear from the front, I noticed two small piles of water boatmen on the seat right where Don and I had been sitting. We had so many of the little devils go down our necks, that they had eventually spilled out the back of our shirt tails onto the seat. The males are interesting in that they have a characteristic row of pegs on the front tarsi, or palae , the pattern of which is distinctive for each species. The males of some species also stridulate to produce a species specific auditory signal. Water boatmen are primarily phytophagous, and feed on algae and gunk that they scoop up with their palae, which have strong rows of long bristles. In the process, they inevitably gather up small animals such as protozoans, nematodes and rotifers, which they eat indiscriminately along with the algae. Water boatmen are often present in enormous numbers, and they may be fed upon extensively by fish under these circumstances.
5. Order - Megaloptera (=Neuroptera in part) Meg-a-LOP-ter-a This is the first order treated here that is holometabolous. That is, the larva is very different from the adults in appearance and ecology. They undergo complete metamorphosis, via the pupal stage, before emerging as an adult. The Neuroptera is a catch-all order, with a variety of quite different looking animals included. Some researchers separate the alderflies and dobsonflies into a separate order, the Megaloptera (Meg-a-LOP-ter-a). The rest of the families are included in the Neuroptera in the more strict sense. They are generally soft-bodied as adults, and although the adults have four well developed wings, they are not what you would call strong fliers. Some, for example the antlions, look down right ungainly in the air. There are at least 10 families of neuropterans in Manitoba, three of which are aquatic in their juvenile stages. The wings are usually similar in size and shape, with many veins and cross-veins (neuro=veins; ptera=wings). Typically, the veins tend to fork just before reaching the outer wing margin, but this isn = t so evident in the aquatic members. The wings are held tent-like over the abdomen at rest, and there are no cerci evident at the tip of the abdomen. All species have chewing mouthparts as adults, though in some, they have no feeding function. Most larvae also have chewing mouthparts, with a few interesting exceptions, for example the spongillaflies, whose larvae have needle-like mouthparts adapted for feeding on freshwater sponges.
Family - Sialidae (alderflies); Si-AL-i-dae There is considerable disagreement as to whether the Megaloptera should treated as a separate order, or as a suborder of the Neuroptera. Either is acceptable. I have treated it separately here, though many authors lump it with the Neuroptera. There is only one species of alderfly in Manitoba, but it is commonly encountered in most of our medium and large rivers and streams, and lake shorelines. The larvae are predacious and live among rocks and debris on the stream bottom. They are distinctive in appearance with their 7 pairs of lateral tubercles and terminal filament. Mature larvae leave the water to pupate in individual cells excavated in the soil. The adults emerge in June, and can be collected by sweeping the riparian vegetation during the day. The alimentary tract is atrophied, and adults are restricted to taking small amounts of liquid foods. During courtship, adults apparently communicate with one another by tapping the substrate or vibrating their abdomens, much in the same manner as the stoneflies. Females deposit large masses of up to 900 orange eggs in neat patches on vegetation overhanging the water. The newly hatched first instar larvae swallow air to form a bubble in the gut, and then drop into the water, where they may drift along for a considerable distance before settling to the bottom.
Family - Corydalidae (dobsonflies); Cor-y-DAL-i-dae We have no confirmed records for any species in this family for Manitoba. However, we have several specimens collected in northwestern Ontario, and it is only a matter of time before their presence here is established. This family includes the mighty hellgrammites or toe-biters that every serious fisherman would at least have heard about. The true hellgrammite, Corydalus cornutus (Linnaeus) , is common in the fast moving, gravel-bottom streams of eastern North America. The adults are impressive, especially the males, which have wicked-looking, sickle-shaped mandibles. The larvae, the hellgrammites, are formidable predators, feeding on a variety of invertebrates in the streams. They are aggressive when disturbed, and once they latch on to your finger, they seem quite unwilling to let go! I was observed a mighty battle between a painted turtle and a hellgrammite. It was a draw, but the poor turtle refused to eat live insects for weeks afterwards. The dobsonfly most likely to be found in Manitoba belongs to the genus Chauliodes . They are considerably smaller than the hellgrammite, though the larvae are predacious, and will take invertebrates as well as small fish and tadpoles. These dobsonflies are restricted to standing water, usually small ponds, and the larvae are easy to recognize, with many lateral filaments on the abdomen, and a pair of respiratory tubes extending from the end of the abdomen.
6. Order - Trichoptera (caddisflies) Tri-CHOP-ter-a This is an important group of aquatic insects, the adults of which are mainly nocturnal, and which look very much like moths. The antennae are usually quite long, the wings and body are covered with hairs (tricho=hair; ptera=wing), and the wings are held tent-like over the back when at rest. The adults vary considerably in size and colour (pale cream-coloured to black; uniformly-coloured to salt and pepper). The larvae are highly adapted and variable in appearance and our 10 families are found in many kinds of aquatic habitats. There are a few massive, hulking predacious species that are generally free-living and free-ranging in streams and rivers. The truly great innovation in the larval caddisflies, however, is the use of silk. Silk is spun by some species into elaborate capture nets hung in the current to filter out suspended food items. Silk is used by most species to construct a case which surrounds the thorax and abdomen of the larva. Plant materials, stems, leaves, and bark, or sand grains, small stones or even snail shells may be incorporated and fastened together with adhesive silk. Cases may be straight, curved, slipper-shaped, or helical. Some of the microcaddisflies spin a tiny milk-bottle shaped case almost entirely of silk. The larvae are free-living, and crawl around on the substrate carrying their portable case with them. We have over 150 species of caddisflies recorded in Manitoba, but additional study will undoubtedly increase this number. The adults of many species are nocturnal and fly readily to lights. They have reduced mouthparts, so the life expectancy for most species is not long. At times, the adults may emerge in enormous numbers from favourable habitat, sometimes causing interesting problems. When Expo 67 was held in Montreal, there was a great deal of concern about the number of caddisflies that emerge from the St. Lawrence River. They even contemplated the application of pesticides to the river to reduce populations and annoyance to visitors at the fair. In Manitoba, some hydropsychid caddisflies are known to emerge in such numbers from the inside walls of turbines in electrical generating stations, that the workers develop severe respiratory allergies to the tiny scales from the wings of the adults. There is a great deal of research to be conducted on this group of insects, on life histories, behaviour, physiology, and their role in aquatic ecosystems.
References to Manitoba Trichoptera: Flannagan, J.F. 1978. Emergence of caddisflies from the Roseau River, Manitoba. In: Proceedings of the 2nd International Conference on Trichoptera. (Ed.) M.I. Crichton, Dr. W. Junk, The Hague. pp. 183-197. Flannagan, J.F. and D.G. Cobb. 1981. Changes in the profundal Trichoptera of Lake Winnipeg 1928-32 to 1969. In: Proceedings of the 3rd International Conference on Trichoptera. (Ed.) G.P. Moretti, Dr. W. Junk, The Hague (Series Entomology 20). pp. 67-74. Ruiter, D.E. 1995. The adult Limnephilus Leach (Trichoptera: Limnephilidae) of the New World. Ohio Biological Survey, Ohio State University, Columbus. Schmid, F. 1980. The insects and arachnids of Canada. Part 7. Genera of the caddisflies of Canada and the adjacent United States. Agriculture Canada Publication 1692. Stiege, S. 2004. Abundance, diversity and seasonality of adult Trichoptera in and around hydroelectric generating stations along the Winnipeg River. M.Sc. Thesis. Department of Entomology, University of Manitoba. xi + 138 pp. There is a copy of this thesis in the Dafoe Library at the University of Manitoba. You are welcome to visit the library and examine the thesis, in which there is information on emergence times for many species of caddisflies found in the Winnipeg River. Wiggins, G.B. 2005. Caddisflies, the Underwater Architects. University of Toronto Press, Toronto. 292 pp. Wiggins, G.B. Larvae of the North American caddisfly genera (Trichoptera). 1996. 2nd Edition. University of Toronto Press, Toronto. Wiggins, G.B. 1998. The caddisfly family Phryganaeidae (Trichoptera). University of Toronto Press, Toronto.
7. Order - Coleoptera (beetles) Col-e-OP-ter-a It is extremely difficult to make generalizations about the Coleoptera, which probably contains more species than any other order. In a survey in the tropical rainforests of Peru, one researcher discovered over 4,000 species of beetles in an area half the size of a football field! In Manitoba, there are more than 80 recorded families. Beetles contain species which are among the smallest and largest insects known. The most distinctive character for recognition of beetles is the modified forewings to form the thickened and sheath-like elytra (coleo=sheath; ptera=wing). These elytra usually meet along the midline of the abdomen, and may extend all the way to the tip of the abdomen. In some families, the elytra are shortened, leaving all or part of the abdomen exposed. The large, membranous hindwings, when present, have characteristic nodes at which they fold up under the elytra. Aquatic beetles carry air in the space under their elytra when they swim beneath the surface. If you sit quietly by the side of a pond, you will see these beetles swimming rapidly to the surface, breaking the surface, and swimming back down as they replace the air in the bubble. The beetles have chewing mouthparts, with well developed mandibles. These mandibles are variously modified depending on the feeding mechanics of the animal. There is tremendous disparity among the various morphological adaptations, including antennae, legs, and general body configuration. Beetles are found in a tremendous variety of habitats. They may be aquatic, semi-aquatic, terrestrial or arboreal; they may be scavengers, detritivores, fungivores, herbivores, predators, parasitoids, or parasites of vertebrates. To complicate matters, juvenile forms are as distinctive as the adults, and the larvae may not conform to the habits of adults of the same species. Anyone who cultures an interest in this group can count on a lifetime of fascination with challenging problems.
Family - Haliplidae (crawling water beetles); Ha-LIP-li-dae Haliplids are curious little beetles with enormous coxal plates which extend over a good portion of the ventral abdomen. We have at least 13 species in Manitoba, but considerable work on the group in North America is desperately needed. The adults are not well adapted for swimming, but rather scramble around on the substrate and in the vegetation. When you do see them swimming through the water, they look like their legs are working a lot harder than their speed would indicate. Both adults and larvae feed primarily on algae and plankton. They are found mostly in ponds and still water, but Brychius spp. occur in fast-moving streams. Only one species, Brychius hornii , is found in Manitoba, in some of the small streams near Riding Mountain.
Family - Dytiscidae (predacious diving beetles); Dy-TISC-i-dae This is the most diverse family of aquatic beetles in the province, with nearly 150 species recorded so far. They are found in a wide variety of habitats: temporary pools, ponds, lakes, rivers, streams, springs, and bogs. Some species are found only in specific habitats, especially those in springs and saline lakes. The range in size of adults is impressive, the smallest ( Liodessus ) being barely 3mm long, with Dytiscus at the other end of the scale at 40mm. You can imagine that the larvae of Dytiscus spp. are aptly called "water tigers"! The adults and larvae are primarily predators, sometimes being quite specific in their prey selection. The larvae of some species, for example, feed only on caddisfly larvae. They locate the caddisfly in its case, and then cling to the case until the larva sticks out its head, embedding its hollow mandibles into it. Digestion is partially external, and the liquefied contents are sucked up. From time to time, dytiscids have been proposed as biological control agents for mosquitoes. Dytiscus spp. have been known to cause significant mortality to pickerel fry being raised in the pothole lakes of central Manitoba. Most of our Manitoba species overwinter as adults, and occasionally become trapped in the ice on the surface of ponds and stream. Imagine my surprise when I picked out some of these adults, and found that when they were brought back to the lab and thawed out, they were still alive and started swimming around.
References to Manitoba Dytiscidae: Larson, D.J. 1975. The predaceous water beetles (Coleoptera: Dytiscidae) of Alberta: systematics, natural history and distribution. Quaestiones Entomologicae 11: 245-498. Larson, D.J., Y. Alarie and R.E. Roughley. 2000. Predaceous diving beetles (Coleoptera: Dytiscidae) of the Nearctic Region, with emphasis on the fauna of Canada and Alaska. NRC Research Press, Ottawa, Ontario, Canada. xiv + 982pp.
Family - Gyrinidae (whirligig beetles); Gy-RIN-i-dae The whirligig beetles are about the most distinctly modified beetles you are likely to see. There are 22 species recorded in Manitoba, all of which are shiny jet black. Their front legs are carried out in front of the body, while the other two pairs are greatly reduced to form strange paddle-like appendages. The antennae are short and compact, and are used to detect vibrations created by insects trapped in the surface tension. They secrete specialized surfactants which help keep them afloat as they spin and twirl across the water surface. Perhaps strangest of all are the compound eyes which are divided laterally so that the upper half views the terrestrial world while the lower half views life in the water. They seem to swim aimlessly on the surface, often in large aggregations of hundreds of individuals in a multispecies swarm. Very often what you see on the surface is only the tip of the iceberg. There may been even more beetles swimming beneath those on the surface. Sometimes when you see these large surface aggregations, they seem to sparkle with the sun reflecting off their shiny backs. As they cruise lazily around, they would seem to be easy prey for fish, but they produce a potent defensive secretion for their self preservation. Just ask any entomologist who has ever used a mouth aspirator to collect water beetles what happens when they suck up a few gyrinids.
Family - Hydrophilidae (water scavengers); Hy-dro-PHIL-i-dae First of all, not all hydrophilids are aquatic. In the subfamily Sphaeridiinae, there are 14 species in Manitoba, all of which are terrestrial, and are found in decaying vegetation, organic matter or animal faeces. The remaining 50 species of hydrophilids in Manitoba, in six subfamilies, are aquatic. They are found mainly in shallow ponds and lakes, and most are just pathetic swimmers. The adults and larvae paddle and tumble around in the water as if they don't belong there at all. The larvae are predacious, and some species seem to hang at the surface of the water, nabbing passing invertebrates. The adults are hampered by a large bubble of air carried in a ventral concavity of the body, but they are able to exchange air at the surface very efficiently. Where the dytiscids rise to the surface posterior end first, the hydrophilids rise head first. They have long palps which are used to break the surface tension, and to create an air channel connecting to the main ventral bubble. As you would guess from their common name, the adults are mainly scavengers.
References to Manitoba Hydrophilidae: Smetana, A. 1988. Review of the Hydrophilidae of Canada and Alaska (Coleoptera). Memoirs of the Entomological Society of Canada, No. 142.
Family - Elmidae (riffle beetles); ELM-i-dae I have included this interesting family of beetles because they so sharply contrast with the other families of aquatic beetles. We have only 7 species recorded for the province, but our fauna is very poorly known, and undoubtedly there are several more species remaining to be discovered here. Adult elmids are covered by an extremely dense pile of minute hairs that traps a thin layer of air, and allows exchange of respiratory gases to take place. So efficient is this mechanical gill, that when an elmid submerges, it can remain submerged for its entire adult life, as long as oxygen in the surrounding water is not depleted. Consequently, elmids are found almost exclusively in the gravel at the bottom of fast flowing rivers and streams. Adults and larvae feed on algae, diatoms, and decaying organic matter. It is interesting that whenever you collect elmids, all stages of larvae and adults are present at the same time. We have very little information on the life history or distribution of our Manitoba species, and there is a lot of interesting work to be done with this group.
8. Order - Diptera (true flies) DIP-ter-a The true flies are an extremely large order of insects and are represented by at least 88 families in Manitoba. The adults are characterized by having only two wings (the forewings) with the hindwings reduced to club-shaped halteres , used for balance (di=two; ptera=wing). They have sucking mouthparts, modified for sponging and lapping, or for piercing. In some families the mouthparts are reduced or completely absent. The larvae are legless (sometimes with prolegs) and the head capsule may be well developed or reduced to a complex of mouth hooks. Flies are found in almost every conceivable habitat. This order contains some of our most annoying pests of man and animals, and important vectors of disease-causing pathogens. There are important pests of cultivated crops, predators, scavengers and nectar feeders. Some species have larvae with the disgusting habit of feeding on the flesh of living vertebrates, causing a condition known as myiasis . Larvae of some species are aquatic, with unusual representatives found in hot springs, glacier-fed streams, saline lakes and sloughs, and even pools of crude oil. There are many peculiar looking species that are wingless as adults, and are inhabitants of the nests of ants, bees and termites. A number of species are ectoparasites of mammals and birds.
Family - Tipulidae (crane flies); Tip-UL-i-dae This is the largest family of Diptera, with well over 14,000 described species, at least 1,525 of which are found in North America. Our knowledge of the Manitoba species is only fragmentary. Many students hesitate to collect crane flies, despite their great diversity. The main reason is that when they are pinned or pointed, the first thing that happens is that their great, beautiful, long legs all fall off! You might as well break them all off right from the start and glue them onto a card with the specimen. As you would guess for such a richly diverse group of insects, generalities are hard to make, and only a small portion of the species are in fact aquatic. These species are found in fast flowing water, ponds and lake margins, intertidal zones and brackish water, mosses and bogs, and even thin films of water running over vertical cliff faces. The larvae feed mainly as shredders and detritivores and are extremely important in energy transfer in aquatic ecosystems. The length of larval development varies from a few weeks to several years in high altitude or high latitude habitats. The spindly-looking adults often strike fear into the hearts of people who believe that they are giant mosquitoes. Others take comfort in knowing that they eat mosquitoes, and even call them "mosquito hawks". Both interpretations are incorrect as it happens. No one has ever seriously studied crane flies in Manitoba, but such an undertaking would be rewarded by many exciting discoveries.
Family - Chironomidae (midges); Chi-ro-NOM-i-dae This is also an extremely diverse family, with over 300 species recorded for Manitoba, though this is surely short of the actual number. Nearly all species are aquatic, but there is a number of terrestrial species which breed in accumulations of decaying organic matter and animal dung. The adults vary in size, but are generally conservative in variation. Some species form mating swarms consisting mainly of males, and as the females are attracted to the swarms, males compete for their favour. Along the shore of Lake Winnipeg and Lake Manitoba, it is not unusual to see great swarms that look like smoke from a distance over the tree tops. As you get close, the hum from the beat of millions of tiny wings is awesome. At this time, insectivorous birds feast on this abundant and readily available food source, and we find some of the highest densities of nesting birds found anywhere in the world on these southern beach ridges. It is the larvae in which we see the greatest degree of specialization. Most species have larvae which construct fine silk tubes in which to live. These tubes are attached to the substrate, to vegetation, and even to the surfaces of other aquatic invertebrates. There are several predacious chironomid larvae, but most feed on fine particulate organic matter which they gather up or filter from the water column using elaborate silken nets. Chironomid larvae can be present in incredible densities of several thousands per square metre and are an important food source for fish and other aquatic insects. Because of their diversity and sensitivity to changes in the environment, chironomids have been shown to be excellent indicators of water quality, by their current community structure, and also by their fossil remains in deep sediments.
References to Manitoba Chironomidae Oliver, D.R. and M.E. Roussel. 1983. The insects and arachnids of Canada. Part 11. The genera of larval midges of Canada. Diptera: Chironomidae. Agriculture Canada Publication 1746.
Family - Stratiomyidae (soldier flies); Strat-i-o-MY-i-dae The soldier flies are a relatively small family of Diptera, with only just over 250 species described for North America. However, only about half of these are aquatic, the rest being found in moist soil and organic matter, manure and accumulated animal wastes, and under tree bark. The larvae of the aquatic species are easily recognized, because, they have a rosette of long stiff hairs around the posterior spiracles. When they rise to the water surface to breathe, the rosette spreads, and forms a conical air passage to the spiracles, and a point of attachment to the surface. They are also somewhat flattened, and the cuticle is granular. The adults are usually brightly coloured, yellow, black and green, and some species are brilliant metallic green. Adults are sometimes quite abundant and are most often seen in numbers on flowers, feeding on nectar. In Manitoba, one of the best plants on which to find adult stratiomyids is cow parsnip, and other large Umbelliferae in wet meadows.
Family - Dolichopodidae (long-legged flies); Dol-i-cho-POD-i-dae This family of beautiful little flies is quite large and there are approximately 500 aquatic species in North America. The adults are very distinctive, being metallic green, black, bronze or purple. The males especially have some bizarre structural modifications related to their complex mating behaviour. In many of our species, there are expanded tarsal segments that are used by the males to signal to prospective mates; like semaphore. The first time I prepared specimens of these species for study, and before I examined them under the microscope, I thought these structures were bits of debris, and I kept trying to pluck them off using my forceps! These males take up prominent positions in the habitat, defend their patch against competing males, and those which are most successful pass their genes on to a greater proportion of the offspring in the next generation. Both adults and larvae are predacious, at least for those species where feeding habits have been described. There are a number of interesting species which as adults walk on the surface of mosquito breeding sites, and pluck mosquito larvae from the water when they surface to breathe.
Family - Culicidae (mosquitoes); Cu-LIC-i-dae You might think that all Manitobans need to know about mosquitoes is that there can be a lot of them! In fact, apart from their abundance in the province, there are at least 45 different species recorded. Most of these belong to the genera Ochlerotatus and Aedes , which include our most important pest species. Aedes and Ochlerotatus larvae develop in snow-melt pools, spring runoff, summer floodwater, or tree holes. All of these species overwinter as eggs, and hatch under suitable environmental conditions of water levels and temperature. The larvae are aquatic, and have a long breathing tube (called a siphon ) on the end of the abdomen, through which they take in air directly from the surface. The pupae are comma-shaped, very active, and they breathe air at the surface, but through a pair of respiratory trumpets on the top of the thorax. The adult females may feed on blood, though as you travel toward the tundra regions of Manitoba, there may be a higher incidence of autogeny ( i.e. females can lay eggs without a blood-meal). One hypothesis for this phenomenon is that in the north, potential hosts are less predictable, and weather conditions more often restrict flight periods for blood-seeking females. Therefore, females that can reproduce without the requirement for blood, at least for the first batch of eggs, will be more successful. There are several other genera of mosquitoes in Manitoba. Culex and Culiseta deposit their eggs in rafts which float on the surface of semi-permanent pools, and the larvae hatch directly into the water. Culex tarsalis Coquillett is rarely as abundant as the Aedes mosquitoes in Manitoba and has little nuisance status. However, it is considered to be the primary vector of the Western Equine Encephalitis Virus to horses and humans and is the target of surveillance using light traps and flocks of sentinel chickens. The recent introduction of West Nile Virus into Manitoba has greatly increased interest and concerns about mosquitoes as vectors of this pathogen. Culex tarsalis is of concern as a primary vector of this pathogen to humans, while a species of mosquito that feeds mainly on birds, Culex restuans Theobald , is also important in the epidemiology of the pathogen. West Nile Virus is especially pathogenic to some species of birds in Manitoba, the corvids, for example. The long-term impact of on populations of these birds is a important matter conservation efforts in the future. Anopheles spp. are found in weedy, permanent water, and include the species of mosquitoes known to transmit the malaria parasites to vertebrates. Fortunately, we don't have human malaria in Manitoba, though there are species found in birds. Mansonia perturbans (Walker) is an unusual species found in permanent marshes and slow-moving streams. It is a savage mosquito, and is most active just after dark during mid summer. The larvae are bizarre because they have abandoned the mode of surface respiration, and rather have a special attachment on the abdomen that allows them to tap into the stems of aquatic plants and take oxygen directly from the plant tissues. Wyeomyia smithii (Coquillett) is our only entirely autogenous species of mosquito. These delicate adults lay their eggs inside the leaves of purple pitcher plants, which grow only in acid sphagnum bogs. Also peculiar for Manitoba mosquitoes, W. smithii overwinters as a larva, frozen into a core of ice inside the pitcher plant leaf beneath the snow.
References to Manitoba Culicidae Darsie, Jr., R.F. and R.A. Ward. 2004. Identification and geographical distribution of the mosquitoes of North America, North of Mexico. University of Florida Press. Wood, D.M., P.T. Dang and R.A. Ellis. 1979. The insects and arachnids of Canada. Part 6. The mosquitoes of Canada. Diptera: Culicidae. Agriculture Canada, Publication 1686,
Family - Simuliidae (black flies); Si-mu-LI-i-dae Canada is notorious for its black flies. Poems have been written about them; they have been immortalized in song. Anyone who has spent time outdoors in the north and boreal regions of Canada, and especially those of you who like to fish rivers, have learned to hate these fierce little devils, that at times seem like hungry dust. My grandfather always maintained that a black fly would cut a piece of flesh from your body and then fly away with it to eat its meal while sitting on a fence post! This is not quite true, even though it might feel like it sometimes. Rather, the female black fly uses its mouthparts to create a wound in the skin, and then it laps up the blood as it pools in the wound. This is in contrast to the mosquitoes, which have needle-like mouthparts that are inserted directly into the blood vessels. The saliva of many species contains anticoagulants, so that after they finish feeding, the blood continues to flow from the bite wound. On one memorable fishing trip along the Credit River in Ontario, I didn't catch any fish, but the squishy noises coming from my boots turned out to be blood from black fly bites rather than water. Our 50 or so species of black flies breed exclusively in running water, and the larvae are highly adapted to survive in this challenging habitat. They attach themselves to the substrate using a circlet of hooks which latches into a patch of silk laid down especially for this purpose. The larvae are essentially legless (though they do have one anterior proleg), but have enlarged feeding fans with which they filter passing organic matter from the water column. Next time you find yourself along the banks of a fast-moving stream, have a look at the trailing vegetation, or pick up smooth rocks in fast water, and I can almost guarantee that you will see black fly larvae wriggling over the surface. They pupate directly on the substrate, often inside slipper-shaped, silken cocoons, and emerge into a gas bubble which rises to the surface and releases the adult directly to the air. Some species are partially or entirely autogenous, but it is the blood-feeders that cause significant annoyance and economic losses to humans, livestock and wildlife. Black flies are recorded as causing death in cattle and wildlife on the Canadian Prairies. Some species are so abundant that they suffocate their hosts by clogging the nose and throat, while Simulium arcticum has saliva that seems to cause anaphylactic reactions in some breeds of cattle. There are pathogens that are transmitted by black flies to humans in some parts of the world. The nematodes that cause river blindness in West Africa have black flies which serve as their vectors. Fortunately, we don = t have any such pathogens in Manitoba which are transmitted to humans by black flies. There is a malaria-like pathogen that black flies transmit to waterfowl in some parts of the province.
References to Manitoba Simuliidae Adler, P.H., D.C. Currie and D.M. Wood. 2004. The black flies (Simuliidae) of North America. Cornell University Press and the Royal Ontario Museum, Toronto. Crosskey, R.W. 1994. The Manitoban blackfly fauna with special reference to prospections made in 1983-1985 in central and southern Manitoba (Diptera: Simuliidae). Journal of Natural History 28: 87-107.
Family - Tabanidae (horse flies, bulldogs, deer flies); Ta-BAN-i-dae The 50 species of tabanids in Manitoba have been the subject of research for many years. The Manitoba Horse Fly Trap, was first developed here at the University of Manitoba by A.J. Thorsteinson and his colleagues in the 1960's, and is now the standard means of collecting and studying this group of flies all over the world. The tabanids can be very broadly divided into two groups, the horse flies and the deer flies. The horse flies include Hybomitra and Tabanus spp., which are large and robust, attack mainly large animals, and which inflict major pain with their bite. They can be serious pests of pastured cattle, horses, and wildlife. I have seen moose come charging out of the forest onto the road and run for their lives, trying to escape these persistent hunters. If you have ever parked a vehicle at the roadside where these flies are abundant, you know that it is wise to keep the windows rolled up! Deer flies ( Chrysops spp.), on the other hand, are smaller, with darkly patterned wings, and which sit at rest in a delta design. These flies also have a painful bite, but in particular fly around the head and shoulders causing considerable annoyance just by their presence. You know they are going to nail you...it's just a matter of when. We do have a few other unspecified genera of tabanids in the province, Atylotus spp., for example. However, these species are rarely encountered, are of no economic consequence, and therefore have attracted little attention. Some of them are entirely autogenous, and never take a blood meal. The larvae of tabanids are aquatic, or at least are found in wet soils. Many are predacious, and have savage mouthparts. If you try to pick up larvae of the larger species, they have the ability to lacerate the skin and draw blood. They feed on other invertebrates in the habitat, including their conspecifics. There are published records of larger larvae attacking and feeding upon small vertebrates, toads, for example.
References to Manitoba Tabanidae McElliggott, P.E.K. and T.D. Galloway. 1991. Seasonal distribution and parity of host-seeking horse flies (Diptera: Tabanidae) from a pasture near Seven Sisters, Manitoba. The Canadian Entomologist 123: 361-370. McElliggott, P.E.K. and T.D. Galloway. 1991. Daily activity patterns of horse flies (Diptera: Tabanidae: Hybomitra spp.) In northern and southern Manitoba. The Canadian Entomologist 123: 371-378. Ralley, W.E., T.D. Galloway and G.H. Crow. 1993. Individual and group behaviour of pastured cattle in response to attack by biting flies. The Canadian Journal of Zoology 71: 725-724. Teskey, H.J. 1990. The insects and arachnids of Canada. Part 16. The horse flies and deer flies of Canada and Alaska. Diptera: Tabanidae. Agriculture Canada Publication 1838.
CONCLUDING REMARKS This is a very superficial treatment of aquatic insects in Manitoba, but I hope that it will lead you into the topic. You can appreciate that the amount of research conducted right here in Manitoba is quite limited, especially that on the emergence patterns of aquatic insects in our rivers, streams and lakes. This is the information that is of greatest value to you as a fly fisher. There is no way to beat the information you collect yourself as you travel around the province and collect in different habitats, so keep detailed notes on what you see in various habitats to build up your own database. Ultimately, this will be one of your most valuable resources, especially for those bodies of water in which you fish often. I have provided a couple of references below on aquatic insects. These references are valuable if you intend to attack this topic seriously, and to build up comprehensive emergence calendars. I have chosen references that have lots of figures and will help you identify the insects you see.
Clifford, H.F. 1991. Aquatic invertebrates of Alberta. University of Alberta Press, Edmonton, Canada. 538 pp. (This textbook is a general overview of invertebrates in the freshwater ecosystems of Alberta. It is quite well illustrated and although of specific reference to species in that province, there is value in its general treatments for species found in Manitoba.) Lehmkuhl, D.M. 1979. How to know the Aquatic Insects. Wm. C. Brown Co. Publishers. Dubuque, Iowa. ( This is a very handy field guide, and in particular, the pictorial keys are practical and easy to use once you are familiar with a few basic characteristics of insect anatomy. It is a spiral bound edition which is convenient to use because it lies flat on the bench.) Martin, J.E.H. 1977. The insects and arachnids of Canada. Part 1. Collecting, preparing, and preserving insects, mites, and spiders. Agriculture Canada Publication 1643. (This is the very first publication in the Insects and Arachnids series initiated by Agriculture Canada many years ago. This is the most compete compendium on collection and preservation techniques that I know. If you decide to collect aquatic insects (or any insects for that matter) seriously, this guide will become indispensable.) McCafferty, W.P. 1981. Aquatic entomology. The fishermen = s and ecologists = illustrated guide to insects and their relatives. Jones and Bartlett Publisher, Inc., Boston. (This is an excellent overview of the aquatic insects and other invertebrates found in freshwater. There are many illustrations, and there is a glossary to assist with your understanding of some of the more technical terms. There is also a table in the back in which the author has listed the various species of mayflies accompanied by the names applied by fishers for the flies, according to species.) Merritt, R.W. and K.W. Cummins (editors). 1996. An introduction to the aquatic insects of North America. 3 rd Edition. Kendall/Hunt Publishing Co., Dubuque. (This is the most comprehensive treatment of the aquatic insects of North America. There are heaps of illustrations, and identification keys to all the families and genera of insects known to occur here. This book is a must for anyone in North America interested in aquatic insects. The 3 rd edition is soft-covered and spiral bound; this makes it easy to spread on the bench, but I find it a bit floppy to use. I understand that a 4 th edition is in the mill, but we probably won = t see it at least until 2009.) Peckarsky, B.L., P.R. Fraissinet, M.A. Penton and D.J. Conklin, Jr. 1990. Freshwater macroinvertebrates of northeastern North America. Cornell University Press, Ithaca. (This volume is not as well illustrated as some of the others that I have cited here, but there are excellent keys for some of the non-insect aquatic invertebrates that you may find useful.) Resh, V.H. and D.M. Rosenberg (editors). 1984. The ecology of aquatic insects. Praeger Special Studies, Toronto. (This collection of chapters written by various authors is a little more technical and specialized, but it has perhaps the best synthesis of information on aquatic insects that you will find anywhere. The editors did a terrific job of keeping the authors focused on their chapter objectives, that the whole book has a really coherent feel to it. There are chapters on insect behaviour, fish predation on aquatic insects, habitat management, and interactions between aquatic insects and humans, among other chapters. If you ever wanted to know more about water and how if shapes the landscape, there is a magnificent chapter by Bob Newbury. He has made an extremely complex and technical subject understandable. You will never look at a stream or shoreline the same again after reading his chapter.) Usinger, R.L. (editor). 1968. Aquatic insects of California, with keys to North American genera and California species. University of California Press. Berkeley. (The illustrations in this volume are not consistently good, and the nomenclature for the aquatic insects is hopelessly out of date. However, I have included it here because Usinger was the first person who tried to synthesize what was known about the aquatic insects in North America, and it was this volume that spawned a generation of interested aquatic ecologists and taxonomists who contributed to what we know today. This one is a classic!) Williams, D.D. and B.W. Feltmate. 1992. Aquatic insects. C.A.B. International, Wallingford. (This is a good general treatment of the biology of aquatic insects. There are introductory chapters on th |